• 한국수소및신에너지학회논문집
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• 제22권3호
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• pp.402-408
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• 2011

Organic Rankine cycles (ORC) can be used to produce power from heat at different temperature levels available as geothermal heat, as biogenic heat from biomass, as solar or as waste heat. In ORC working fluids with relatively low critical temperatures and pressures can be compressed directly to their supercritical pressures and heated before expansion so as to obtain a better thermal match with their heat sources. In this work thermal performance of ORC with and without an internal heat exchanger is comparatively investigated in the range of subcritical and transcritical cycles. R134a is considered as working fluid and special attention is paid to the effect of turbine inlet pressure on the characteristics of the system. Results show that operation with supercritical cycles can provide better performance than subcritical cycles and the internal heat exchanger can improve the thermal efficiency when the temperature of heat source becomes higher.

• 한국건설순환자원학회논문집
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• 제5권2호
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• pp.83-90
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• 2010

As a reinforced fabric, asbestos has been utilized as a fire-resistant material as it has a superior flexural stiffness and heat resistance up to $1500^{\circ}C$. However, due to its harmfulness, its use has been prohibited recently and the even the installed asbestos materials are being repaired or supplemented if there is a concern about flying. Asbestos is mainly used for construction panels as a reinforced fabric and coating materials to ensure the fire-resistance of steel frames. Asbestos was used as fire-resistant materials for steel frames until 1991 and then prohibited as Act on Industrial Safety and Health limits the concentration of asbestos in the air. Classified as a designated waste according to Act on Waste Control, asbestos must be buried if there is no possibility of flying (panel-type materials) or cement-solidified and then buried if there is a possibility of flying (spray coating material) In general, it is required that a new waste landfill include a certain landfill facility for designated waste, but in reality there is an absolute storage of landfill facilities for designated waste as they only install facilities of the size required by the regulations. This could result in the 2nd environmental pollution as they cannot process asbestos wastes which will be generated in large volume in the future. This study explores a method that melts asbestos wastes at $700^{\circ}C$ rather than cement-solidifying the waste asbestos from construction sites, especially asbestos-containing spray coating. The study results showed that there was no change in the composition and shape even though asbestos wastes was melted at $1300^{\circ}C$, but there was a change for the specimen which was process in advance for low temperature melting and then melt at $900^{\circ}C$.

• 에너지공학
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• 제21권4호
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• pp.402-410
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• 2012

본 연구에서는 가솔린 엔진 자동차에서 엔진 폐열 회수를 위한 이중 회로 랭킨 사이클 성능 해석이 수행되었다. 고온(HT)의 엔진 배기가스 열회수를 위해서는 물을 사용하는 스팀사이클이 적용되었고, 엔진 냉각수열과 고온 사이클로부터의 응축열을 활용하는 저온(LT) 사이클은 R-134a를 사용하는 유기랭킨사이클이 적용되었다. 고온 및 저온 열원을 동시에 활용하는 이중 회로 시스템의 특성을 파악하기 위해 에너지 및 엑서지 분석이 수행되었다. 고온 및 저온 사이클에 사용되는 용적형 팽창기의 체적이 차량적용을 위한 시스템 최적화에 매우 중요하며 시스템 최적화를 위해서는 반드시 고려되어야 한다. 목표로 하는 엔진 운전 조건에서 고온(HT) 팽창기와 저온(LT) 팽창기의 체적을 고려하면서 고온(HT) 사이클의 팽창비와 저온(LT) 사이클의 응축온도가 시스템의 성능에 미치는 영향을 파악하였다. 본 연구에서는 이러한 이중 회로 랭킨 사이클 시스템에 의해 목표 엔진 운전조건에서 엔진 폐열로부터 약 21%의 추가 동력을 얻을 수 있는 것으로 예측되었다.

• 한국수소및신에너지학회논문집
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• 제26권1호
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• pp.79-87
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• 2015

In a gas engine, the exhaust and the engine cooling water are generated. The engine cooling water temperature is $100^{\circ}C$ and the exhaust temperature is $500^{\circ}C$. The amount of heat of engine cooling water is 43 kW and the amount of heat of exhaust is 21 kW. Eight different hybrid organic Rankine cycle (ORC) system configurations which considering different amount and temperature of waste heat are proposed for two gas engine tri-generation system and are thermodynamically analyzed. Simple system which concentrating two different waste heat on relatively low temperature engine cooling water shows highest thermal efficiency of 7.84% with pressure ratio of 3.67 and shaft power of 5.17 kW.

• 한국주조공학회지
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• 제15권5호
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• pp.477-482
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• 1995

A computer simulation model of various smelting process for melting waste sand was developed by using energy and material balance concept. This model can predict the coal, flux and oxygen consumption and the volume and temperature of off-gas. The major critical variables for smelting process can be explained by using the analysis of energy and material balance. The major conclusions were as follows; 1. The most important variables for smelting process were high post-combustion ratio, high heat transfer efficiency and refractory protection technology. 2. For saving energy in this smelting process, selection of raw materials i.e coal, flux are very important, espacially using of low volatile coal is very profitable. 3. The treatment cost of waste sand is high and environmental restriction is severe, in this reason we must be concerned in the treatment of waste sand by smelting process.

• 청정기술
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• 제23권3호
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• pp.223-236
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• 2017

기후변화 대응을 위한 청정 화력발전 기술의 일환으로 폐기물과 바이오매스를 중심으로 한 신재생연료의 이용이 크게 증가함에 따라 특히 고온 고압 스팀 생산이 필요한 발전용 보일러 열교환기의 고온부식(High temperature corrosion) 문제가 심각한 현안으로 대두되고 있다. 이러한 문제점은 저급연료에 포함된 염화알칼리 성분이 보일러 내 열교환기 중 표면온도가 가장 높은 과열기(Superheater) 또는 재열기(Reheater)에 점착된 후 염소에 의해 부식이 가속화되어 일어난다. 이를 해결하기 위해 설계 변경, 재료 개선, 연료 전처리 등의 고온부식 회피 방법과 함께 첨가제를 이용한 고온부식 방지 기술이 활용되고 있다. 본 연구에서는 보일러에서 고온부식 방지를 위한 다양한 접근 중 특히 첨가제를 이용한 연구개발 현황을 소개한다.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2000년도 THE THIRD INTERNATIONAL CONFERENCE ON AGRICULTURAL MACHINERY ENGINEERING. V.III
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• pp.639-646
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• 2000

Hot air heater with light oil combustion is the most common heater for greenhouse heating in the winter season in Korea. However, since the heat efficiency of the heater is about 80%, considerable unused heat in the form of exhaust gas heat discharges to atmosphere. In order to capture this exhaust gas heat a heat recovery system for plant bed heating in the greenhouse was built and tested in the hot air heating system of greenhouse. The system consists of a heat exchanger made of copper pipes, ${\phi}\;12.7{\times}0.7t$ located inside the rectangular column of $330{\times}330{\times}900mm$, a water circulation pump, circulation plastic pipe and a water tame The total heat exchanger area is $1.5m^2$, calculated considering the heat exchange amount between flue gas and water circulated in the copper pipes. The system was attached to the exhaust gas path. The heat recovery system was designed as to even recapture the latent heat of flue gas when exposing to low temperature water in the heat exchanger. According to performance test it can recover 45,200 to 51,000kJ/hr depending on the water circulation rates of 330 to $690{\ell}$/hr from the waste heat discharged. The exhaust gas temperature left from the heat exchanger dropped to $100^{circ}C$ from $270^{circ}C$ by the heat exchange between the water and the flue gas, while water gained the difference and temperature increased to $38^{circ}C$ from $21^{circ}C$ at the water flow rate of $690{\ell}$/hr. And, the condensed water amount varies from 16 to $43m{\ell}$ at the same water circulation rates. This condensing heat recovery system can reduce boiler fuel consumption amount in a day by 34% according to the feasibility study of the actual mimitomato greenhouse. No combustion load was observed in the hot air heater.

• 설비공학논문집
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• 제13권5호
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• pp.422-430
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• 2001

In the present study, an evaporative generation process of ammonia-water solution film on the vertical plate was analysed. For the utilization of waste heat, hot water of low temperature was used as the heat source. The continuity, momentum, energy and diffusion equations for the solution film and vapor mixture were formulated in integral forms and solved numerically. Counter-current solution-vapor flow resulted in the refrigerant vapor of the higher ammonia concentration than that of co-current flow. Eve the rectification of refrigerant vapor was observed near the inlet of solution film in counter-current flow. For the optimum operation of generator using hot water, numerical experiments, based on the heat exchange and generation efficiencies. revealed the inter-relationships among the Reynolds number of the solution film and hot water, and the length of generator. Enhancement of heat and mass transport in the solution film was found to be very effective for the improvement of generation performance, especially at high solution flow rate.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 춘계학술발표대회 논문집
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• pp.204-209
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• 2011

According to the environment report of UN, korea was classified as potable water shortage countries. Approximately 71% of the Earth's surface is covered by ocean. However, it is difficult to use for industry of residential purpose without a certain processing. The development of solar and waste-heat used absorption desalination technology have been examined as a viable option for supplying clean energy. In this study, the modelling of the main devices for solar and waste-heat used and adsorption desalination system was introduced. The design is divided into three parts. First, the evaporator for the vaporization of the top water is designed, and then the reactor for the adsorption and release of the steam is designed, followed by the condenser for the condensation of the fresh water is designed. In addition, new features based on the energy balance are also included to design absorption desalination system. In this basicresearch, One-bed(reactor) adsorption desalination plant that employ a low-temperature solar and waste energy was proposed and experimentally studied. The specific water yield is measured experimentally with respect to the time controlling parameters such as heat source temperatures, coolant temperatures, system switching and half-cycle operational times.

• 에너지공학
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• 제21권4호
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• pp.398-401
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• 2012

본 연구에서는 자동차용 엔진 폐열 회수 유기랭킨사이클에 적용하기 위해 개발 중인 스크롤 팽창기의 효율을 상용 스크롤 팽창기와 비교 분석을 수행하였다. 팽창기 효율 특성 시험을 위해 유기랭킨사이클을 운전하면서 팽창기 출력, 팽창기 입구 온도, 압력 및 작동유체(냉매 R134a)의 유량을 측정하였으며, 개발 중인 스크롤 팽창기의 전효율은 상용 스크롤 팽창기의 전효율에 비해 매우 낮은 수준을 나타내었다. 특히 팽창기 내부의 작동유체 누설에 의한 체적효율 저하가 전효율 저하에 큰 영향을 주는 것으로 파악되었기 때문에 향후 팽창기 효율 향상을 위해 팽창기 내부의 누설문제를 필히 해결해야할 것으로 분석되었다.